Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J27/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
  • B01J27/14—Phosphorus; Compounds thereof
  • B01J27/186—Phosphorus; Compounds thereof with arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
  • B01J27/188—Phosphorus; Compounds thereof with arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium with chromium, molybdenum, tungsten or polonium
  • B01J27/19—Molybdenum
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
  • C07C51/16—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation
  • C07C51/21—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen
  • C07C51/25—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen of unsaturated compounds containing no six-membered aromatic ring
  • C07C51/252—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen of unsaturated compounds containing no six-membered aromatic ring of propene, butenes, acrolein or methacrolein

Definitions

• This invention relates to the oxidation of unsaturated aldehydes. It deals with a new method of carrying out such an oxidation selectively to produce the corresponding unsaturated carboxylic acid in high yields. Another aspect of the invention deals with improved catalysts for the conversion of unsaturated aldehydes to the unsaturated corresponding acids.
• the invention has particular advantage in the production of acrylic and methacrylic acids.
• Some unsaturated acid can be obtained by oxidizing unsaturated aldehydes with hydrogen peroxide according to U. S. Patent 2,377,584 but large amounts of dihydroxy aldehyde are simultaneously produced in the patented process.
• US. Patents 2,744,928 and 2,744,929 disclose methods by which unsaturated aldehydes may be converted to the corresponding unsaturated carboxylic acid. These methods involve a liquid phase reaction in the presence of a solvent and they require the use of both a catalyst and a peroxidizing agent such as hydrogen peroxide. This process has the disadvantage of involving solvent recovery steps and the use of hydrogen peroxide as a source of oxygen is not as economic as other oxygen sources.
• the unsaturated acids produced according to the process of this invention have wide utility in the plastics industry, either in their free form or as related compounds such as the esters.
• the ethyl and methyl esters of acrylic and methacrylic acids, for example, are in great demand at the present time.
• the process of this invention is carried out by reacting an unsaturated aldehyde with oxygen in the vapor phase in the presence of a catalyst.
• the catalyst employed in this process is a phosphomolybdic acid or salt thereof which may be employed with or without a support.
• Another feature of the process relates to the addition of water in the vapor phase to the reaction zone, but the process is not limited to one in which water is necessarily present in the reaction zone as the desired reaction will occur in the absence of water with some reduction in yield.
• the process of this invention is applicable to the oxidation of a wide variety of unsaturated aldehydes which may be aliphatic, alicyclic or aromatic substituted aldehydes.
• the aldehydes may be substituted by hydroxy, ether, carboxylic acid, carboxylic acid ester, keto, nitro and like groups or halogen atoms.
• the unsaturated aldehyde or unsaturated aldehyde mixture can contain other compounds including saturated aldehydes which may undergo simultaneous oxidation or inert compounds which will not interfere with the reaction.
• the catalyst which is employed in the process of this invention is a phosphomolybdic acid or a salt thereof.
• the free acid is employed and it has the following formula:
• Free acids may be prepared in any of several ways: (1) by mixing appropriate quantities of phosphoric and molybdic acid; (2) by double decomposition of salts;'
• the appropriate phosphomolybdate salt may be made in solution generally after acidifying and heating theoretical quantities of the reactants. Any metallic cation can be used to form the salt,
• dic acid have been found to be preferable. In some instances, it may be beneficial to have an excess of the metallic cation present when a salt is to be employed as the catalyst.
• the phosphomolybdic acid or salt thereof may be employed in an unsupported form, it may also be employed in conjunction with a support. If a support is employed, the final catalyst should comprise at least weight percent of the phosphomolybdic compound and particularly good results are obtained when the final catalyst comprises at least about 50 weight percent of the phosphomolybdic compound. Catalysts comprising 10 percent or less of the phosphomolybdic compound are operable but the conversion level is reduced.
• the preferred support is silica but it is not required that the silica be pure and it may contain varying amounts of alumina. Other inert supports such as titania, zirconium oxide and the like may be conveniently employed.
• the surface area of the catalyst not be too great. It has been observed that a catalyst having a high surface area has a high activity which impairs the selectivity of the catalyst and it may result in the oxidation of the unsaturated aldehyde beyond the desired degree.
• the surface area as measured by conventional methods should be in the range of 1 to 250 square meters per gram and it is preferred that the surface area of the catalyst be in the range of about to about 100 square meters per gram.
• the phosphomolybdic acid or salt thereof may be incorporated on the support by means of either impregnation or co-gelation; however, it is preferred to prepare the catalyst by co-gelling the phosphomolybdic acid or salt thereof with the support.
• the latter method yields a catalyst which has superior activity for the desired reaction and which has a greater degree of homogeneity than the impregnated catalyst.
• it may be beneficial to subject the catalyst to heat treatment after preparation. It has been observed that there is little advantage to employing temperatures of over 1000 F. for such heat treatment.
• Oxygen for the process of this invention may be supplied either in the form of air or as free molecular oxygen and the reaction will proceed to some extent in the absence of added oxygen since the catalyst employed in the process will furnish some oxygen to the reaction, but in the preferred mode of executing the process of this invention additional oxygen is supplied to the reactor.
• Air is the preferred source of oxygen since the nitrogen contained therein serves as a purge gas in the reactor.
• the amount of oxygen fed to the reactor based on 1 mol of unsaturated aldehyde should be in the range of 0.5 to 50 mols, but the best results are obtained when the molal ratio of oxygen to unsaturated aldehyde is about 1:1.
• water has a beneficial effect on the course of the reaction and relatively large quantities of water may be fed to the reactor along. with the unsaturated aldehyde.
• the molal ratio of water to the unsaturated aldehyde may be in the range of 0:1 to 12:1, but a ratio of about 7:1 is preferred.
• the temperature at which the reaction is to be conducted has an effect on conversion; and while temperatures in the range of 500 to 900 F. may be employed, the best results are obtained when the temperature is in the range of about 650 to 750 F. A temperature ofv about 700 F. appears to be optimum for the conversion of acrolein to acrylic acid. Generally, the reaction is carried out at about atmospheric pressure but other pressures are operable.
• the process of this invention may be conducted intermittently or continuously.
• a fixed-bed reactor employing a pelleted form of a catalyst may be employed, and it is also feasible to conduct the process in a reactor containing. a fluidized catalyst bed. Since the reaction. is exothermic, the temperature within the reactor must be regulated in order to control the reaction. It appears that the operation of a fluidized bed reactor offers some advantage from the standpoint of temperature regulation within the reactor.
• catalyst employed in this process is not materially affected by the reaction, and since it is not usually necessary to regenerate the catalyst no provision is ordinarily made for regeneration. However, catalyst regeneration is contemplated within the scope of this invention as certain operations may require such a step.
• the products of this reaction may include carbon monoxide, carbon dioxide, and the unsaturated acid together with any unconverted unsaturated aldehyde.
• the desired product of the reaction namely the unsaturated acid
• Conversion Weight of unsaturated aldehyde in the feed Weight of unsaturated aldehyde in the cfiiuent Weight of unsaturated aldehyde in the feed W'eight of unsaturated aldehyde in the feed Weight of unsaturated aldehyde in the elfiuent In the case where acrolein is the unsaturated aldehyde to be oxidized, the amount of acrolein is determined by treating an aliquot of a solution with excess dinitrophenyl hydrazine or by vapor phase chromotography. Acrylic acid which is the product of the acrolein reaction was determined by titrating an aliquot of an aqueous solution with sodium hydroxide.
• the titrated solution was evaporated to dryness and the salt recovered therefrom was analyzed by infrared for the acrylate.
• the products of the reaction were recovered by scrubbing the eflluent gases from the reactor with cold water;
• Example I '4'Spa'rts'by weight of40-l00 mesh silica gel was calcined at 1800" F; for 18 hours” in order to reduce its The resulting solution is re ferred to in connection with the analyses mentionedsurface area.
• the calcined silica gel was then impreghated with a solution of 5 parts by weight of reagent grade phosphoinolybdic acid r o zoMoo isn o in about 15 parts by weight of water.
• the resulting catalyst was dried in an oven at 210 Rand subsequently heat flat d in a mufiie furnace at 1000 F. for 2 hours. 500 g.
• Example III A bismuth phosphomolybdate catalyst was prepared according to the following procedure:
• a colloidal silica sol containing phosphoric and molybdic acid was prepared according to the procedure outlined in Example II with the addition of cc. of concentrated nitric acid. 80 g. of Bi(NO -5H O were dissolved in a dilute nitric acid solution and this was added to the silica so]. The resulting gel was partially dried and the drying was completed by placing the catalyst in a furnace at a temperature of 1000 F. for a period of 2 hours. The catalyst was then ground and screened to 60-200 mesh.
• Example IV Another phosphomolybdic acid catalyst was prepared according to the following procedure:
• the contact time was 23.5 seconds and the run was continued for 2400 seconds.
• the products of the reaction were recovered by scrubbing the reactor eilluent with water. Analysis of the products of this reaction revealed that 64.8 percent of acrolein in the feed had been converted to other products and the yield of acrylic acid was 35.1 percent.
• Example I V-A In another run with the catalyst of Example IV as other feed stream was reacted under the conditions of Example IV. This feed had the following composition:
• Component Parts by volume Acrolein 10 Air 30 Water 70 7 percent to other useful products (acetic acid and acetaldehyde). The yield of acrylic acid was 78.3 percent.
• a process for the manufacture of an unsaturated carboxylic acid which comprises the step of reacting in the vapor phase at a temperature in the range of 500 to 900 F. an unsaturated aldehyde with oxygen in the presence of a catalyst comprising a phosphomolybdic compound selected from the group consisting of phosphomolybdic acid, bismuth phosphomolybdate, tin phosphomolybdate, and antimony phosphomolybdate.
• a process for the manufacture of an unsaturated carboxylic acid which comprises the step of reacting in the vapor phase at a temperature in the range of 500 to 900 F. an unsaturated aldehyde with oxygen in the presence of water and a catalyst comprising a phosphomolybdic compound selected from the group consisting of phosphomolybdic acid, bismuth phosphomolybdate, tin phosphomolybdate, and antimony phosphomolybdate.
• a process for the manufacture of an unsaturated carboxylic acid which comprises the step of contacting in the vapor phase at a temperature in the range of 500 to 900 F. a mixture of an unsaturated aldehyde and an oxygen-containing gas with a catalyst comprising a phosphomolybidic compound selected from the group consisting of phosphomolybdic acid, bismuth phosphomolybdate, tin phosphomolybdate, and antimony phosphomolybdate.
• a process for the manufacture of an unsaturated carboxylic acid which comprises the step of contacting in the vapor phase at a temperature in the range of 500 to 900 F. a mixture of an unsaturated aldehyde and an oxygen-containing gas with a catalyst comprising a phosphomolybidic compound selected from the group consisting of phosphomolybdic acid, bismuth phosphomolybdate, tin phosphomolybdate, and antimony phosphomolybdatc in the presence of water.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Engineering & Computer Science (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Materials Engineering (AREA)
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• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
• Low-Molecular Organic Synthesis Reactions Using Catalysts (AREA)

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Cited By (27)

Citations (8)

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• 0
  • NL NL104763D patent/NL104763C/xx active
  • NL NL225963D patent/NL225963A/xx unknown
• 1957
  • 1957-03-18 US US646581A patent/US2881212A/en not_active Expired - Lifetime
• 1958
  • 1958-03-17 DE DEST13555A patent/DE1245363B/de active Granted

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